The present invention relates to a developing unit of the type developing a latent image formed on an image carrier by depositing a developing liquid, which consists of a carrier liquid and a developing substance, and a copier, facsimile apparatus, printer or similar image forming apparatus including the same.
A developing unit for use in an image forming apparatus uses either one of a dry powdery developer or a developing liquid. Generally, a developing unit using a developing liquid includes a developing roller rotatable while carrying the liquid thereon. A voltage for development is applied to the developing roller to thereby form an electric field between the roller and an image carrier.
The problem with a developing unit of the type described is that a toner image formed thereby is sometimes irregular. By a series of researches and experiments, I found that irregular development was ascribable to the unstable strength of the electric field. Further, I found that in a so-called contact type developing unit that develops the latent image with the developing roller contacting the image carrier, irregularities on the surface of the roller cause fine irregularities to appear on the surface of the developing liquid deposited on the roller, also making development irregular.